In order to manufacture rotor blades, such as windmill blades or wind turbine blades, it is known to wind roving tapes or roving bundles around a core. The systems described in patents U.S. Pat. Nos. 4,242,160 and 4,381,960 make use of this approach. In order to meet the surface quality that is desired for wind turbine applications and prevent the raw composite material surface from appearing as an external surface, an additional finishing treatment is necessary.
Another approach that allows to ensure a satisfying quality of the surfaces and bonding of the materials, and, at the same time, provides constant material characteristics throughout the blade, is vacuum-assisted resin transfer moulding. In the method proposed in patent EP 1 310 351 B1, materials are positioned in a mould cavity between an inner and an outer mould part, and, after evacuating the mould cavity, resin is allowed to flow in and to bond the materials. 